Lee Hyunho, Sumino Takanobu, Suzuki Takashi, Sano Yutaka, Endo Noriyuki, Chang Yingshih, Fujimaki Hirohisa, Ryu Keinosuke, Nakanishi Kazuyoshi
Department of Orthopaedic Surgery, Nihon University School of Medicine, 30-1 Oyaguchi Kami-cho, Itabashi-ku, Tokyo, 173-8610, Japan.
Department of Orthopaedic Surgery, Eisei Hospital, 583-15 Kunugida, Hachioji-shi, Tokyo, 193-0942, Japan.
BMC Musculoskelet Disord. 2021 Apr 12;22(1):346. doi: 10.1186/s12891-021-04206-8.
Tibial rotational alignment in total knee arthroplasty (TKA) is generally determined based on intra-articular structure, and can be difficult to ascertain in some cases. The aim of this study was to investigate whether the medial tangent angle of the tibia (MTAT) could be useful in determining the anteroposterior axis of the tibia.
This study was performed on 103 lower limbs in 53 patients who underwent primary total hip arthroplasty. The selection criteria for our study were based on the assumption that knees in patients undergoing THA exhibit fewer degenerative changes than knees in patients undergoing TKA. Using computed tomography images, the MTAT, comprising the medial tangent of the proximal tibia and the anteroposterior (AP) axis of the tibia, was measured on three horizontal planes: at the distal edge of the tibial tubercle (A), at 5 cm distally (B), and at 10 cm further distally (C). The tibial medial surface was grouped into three classes according to shape: valley type, flat type, and hill type. The percentage at which these shapes were observed in each group was also calculated. Measurement reliability was calculated using the intraclass correlation coefficient.
The angles were 45.2° (interquartile range: IR 43.0-47.7) at A, 42.7° (IR 38.7-45.9) at B, and 42.4° (IR 38.2-45.9) at C. Intra-rater reliability and inter-rater reliability was 0.982 and 0.974 at A, 0.810 and 0.411 at B, and 0.940 and 0.811 at C, respectively. Regarding the tibial medial surface, the valley type was observed in all cases at A, and the hill type was observed in the highest percentage of cases at B and C.
The MTAT was approximately 45° at level A, and reproducibility was the highest among the three groups. The two points forming the valley on the tibial medial surface were bony ridges. Therefore, the medial tangent of the tibia at level A could be easily determined. Because the distal edge of the tibial tubercle exists at the surgical area and the extra-articular area, it can be a suitable intraoperative, extra-articular landmark in determining the tibial AP axis, even for revision TKA.
全膝关节置换术（TKA）中胫骨旋转对线通常基于关节内结构确定，在某些情况下可能难以确定。本研究的目的是探讨胫骨内侧切线角（MTAT）在确定胫骨前后轴方面是否有用。
本研究对53例行初次全髋关节置换术患者的103条下肢进行。我们研究的选择标准基于这样的假设，即行THA患者的膝关节退变改变比行TKA患者的膝关节少。使用计算机断层扫描图像，在三个水平面上测量MTAT，包括胫骨近端的内侧切线和胫骨的前后（AP）轴：在胫骨结节远端边缘（A）、在其远端5 cm处（B）以及在再远端10 cm处（C）。根据形状将胫骨内侧面分为三类：谷型、平型和丘型。还计算了每组中观察到这些形状的百分比。使用组内相关系数计算测量可靠性。
A处角度为45.2°（四分位间距：IR 43.0 - 47.7），B处为42.7°（IR 38.7 - 45.9），C处为42.4°（IR 38.2 - 45.9）。A处的组内可靠性和组间可靠性分别为0.982和0.974，B处为0.810和0.411，C处为0.940和0.811。关于胫骨内侧面，A处所有病例均观察到谷型，B处和C处观察到丘型的病例百分比最高。
A水平处的MTAT约为45°，三组中其可重复性最高。胫骨内侧面形成谷的两点为骨嵴。因此，A水平处胫骨的内侧切线易于确定。由于胫骨结节远端边缘存在于手术区域和关节外区域，即使对于翻修TKA，它也可以是确定胫骨AP轴的合适术中关节外标志。
